A heat pipe is a heat transfer mechanism that can transfer a large amount of heat with a very small difference in temperature between its hot portion (or higher temperature region) and its cold portion (or lower temperature region). Inside a heat pipe, at the hot portion, a working fluid is evaporated into a vapor, and the vapor flows through a vapor region within the heat pipe and condenses on the cold portion into a liquid. The liquid is then moved through a liquid region within the heat pipe (e.g., by gravity and/or capillary action) back to the hot portion to be evaporated again to repeat the heat transfer cycle. Because heat pipes contain no mechanical moving parts, it typically requires very little maintenance. In addition, as a heat transfer mechanism, a heat pipe has much higher efficiency in transferring heat and is a much better heat conductor than an equivalent solid metal block (or pipe).
In more detail, a typical heat pipe is composed of a sealed housing (or pipe) made of a material with high thermal conductivity such as copper or aluminum. The sealed pipe is evacuated to form a vacuum, and then a portion of the pipe is filled with a working fluid (or coolant). Due to the partial vacuum that is near or below the vapor pressure of the fluid, some of the fluid will be in the liquid phase and some will be in the gas phase.
Inside the pipe's walls, a wick structure may be included to exert a capillary pressure on the liquid phase of the working fluid to wick it back to the hot portion. The typical wick structure may be formed with a foam having random cell configurations or a honeycomb structure. As such, it is difficult or even impossible to fabricate high aspect ratio thin diameter pores with porosity of the desired dimensions. It addition, it is difficult to design a heat pipe that can have both high structural performance as well as high thermal performance.
As such, there is a need for a heat pipe that can be easily manufactured to have high aspect ratio small diameter pores with porosity of the desired dimensions, designed for both high structural performance as well as high thermal performance, and be tailored for a variety of applications.